Chapter 11: Assembler Programs

You should read this chapter if you intend using Assembler programs with IMS Option.

IBM mainframe Assembler language programs are supported by IMS Option when using Mainframe Express Assembler Option. Assembler programs are supported as application programs, secondary index sparse routines, DB data capture exit programs and MFS edit routines.

11.1 Assembler Applications

An Assembler program can be the main program or a called subroutine in an application. For Assembler main programs, IMS Option calls the program and passes the PCB list using standard linkage conventions. That is, register 1 points to the PCB list and the last PCB address has the high-order bit set. A system exit named IMS86ENT can be customized to support alternative conventions. See the chapter Advanced Customization for information on the IMS86ENT system exit.

11.2 Assembler Exit Programs

Secondary index sparse routines, DB data capture exit programs and MFS segment and field exit programs can be written in COBOL or Assembler language. Bypass MFS physical terminal edit routines are only supported in Assembler. For COBOL, IMS Option calls these programs directly and uses standard linkage convention. For Assembler, the parameters passed from IMS Option need to be converted. This parameter conversion is done by an Assembler program named ims2asm.mlc in the IMS Option source folder. When IMS Option needs to call an Assembler exit program, it calls IMS2ASM instead. IMS2ASM converts the parameters into the required format and calls your exit program. See the program comments in ims2asm.mlc for complete details.

There are two System Configuration settings which control the language for these exits. The language for the MFS exits is defined on the TM/MFS page of IMS System properties. The language for secondary index sparse routines and DB data capture exit programs is defined on the DB page of IMS System properties. The TM/MFS and DB pages are accessed from the IMS view by right-clicking IMS System and clicking Properties.